Some users may be unable to load chat history or previously pinned chats, and can't pin chats in Microsoft 365 Copilot

A post-incident report has been published.

A post-incident report has been published.

Title: Some users may be unable to load chat history or previously pinned chats, and can't pin chats in Microsoft 365 Copilot User impact: Users may have been unable to load chat history or previously pinned chats, and couldn't pin chats in Copilot Chat. More info: Previously pinned chats didn't show up for users to select, and chat histories weren't showing up as expected. Final status: The fix is fully deployed across all affected environments and we've confirmed with affected users that impact is remediated. Scope of impact: Some users may have been unable to load chat history, previously pinned chats, and couldn't pin chats in Copilot Chat. Start time: Tuesday, September 1, 2026, at 3:38 AM UTC End time: Wednesday, November 4, 2026, at 12:30 PM UTC Root cause: The pinned chats feature in Microsoft 365 Copilot and Copilot Chat contained a code defect that had been present since the feature was first released. This defect wasn’t caught during testing due to its difficulty to reproduce locally. A recent migration exposed this defect, which, under certain conditions, prevented pinned chats from loading and prevented users from pinning new chats. Next steps: - Please see the post-incident report (PIR) for next steps.

Title: Some users may be unable to load chat history or previously pinned chats, and can't pin chats in Microsoft 365 Copilot User impact: Users may be unable to load chat history or previously pinned chats, and can't pin chats in Copilot Chat. More info: Previously pinned chats don't show up for users to select, and chat histories aren't showing up as expected. Current status: We've identified a recent feature update that introduced an error which is resulting in impact. We've deployed a code fix to address the error and remediate the impact. We're monitoring the rollout of the fix deployment, and the current timeline estimates it will be completed by our next scheduled communication update. Scope of impact: Some users may be unable to load chat history, previously pinned chats, and can't pin chats in Copilot Chat. This information may be updated as our investigation continues. Start time: Tuesday, September 1, 2026, at 3:38 AM UTC Root cause: A recent feature update revealed an error resulting in this impacting event. Next update by: Wednesday, November 4, 2026, at 4:30 PM UTC